Specific class structure comes into existence due to:

Relations of production

Marx understood capitalism as a system of commodity production, or production for the market, through the use of wage labour. As you have already learned, Marx wrote that all economic systems are also social systems. Each mode of production consists of particular relations of production, which in turn give rise to a specific class structure. He emphasised that the economy does not consist of things (goods circulating in the market), but is made up of relations between people who are connected to one another through the process of production